I use these mandrels that are meant for jewelry making: (https://www.amazon.com/Wrapping-Mandel-Working-Jewelry-Forming/dp/B07M7DBKQP/ref=mp_s_a_1_2_sspa?dchild=1&keywords=mandrels+for+jewelry+making&qid=1609688323&sprefix=mandrels&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEySENFWU9YWFQyRERRJmVuY3J5cHRlZElkPUEwODExNzM4SUZNQ1ZTRDFQRFhSJmVuY3J5cHRlZEFkSWQ9QTAwOTAxOTExNURVTVk3RFpUS1MzJndpZGdldE5hbWU9c3BfcGhvbmVfc2VhcmNoX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=)

But like said earlier, drill bits or dowels of different sizes work as well I just wanted something a little cleaner.